Mineral formations, such as iron ore formations, commonly present high values of density contrasts with respect to the hosting environment. In this context, rock density is a key parameter in the estimation of resources and reserves that contribute to geological modeling activities for the purposes of mineral exploration.
With respect to conventional techniques for determining the density of rocks, gamma-gamma geophysical well logging is one technique which provides for methods for direct measurements of density in drilling cores or samples. In gamma-gamma geophysical well logging, density measurements are performed inside the borehole, also referred to as in-situ. The record of these density measurements is acquired at a centimeters pace, ensuring ore volume is not overestimated.
However, gamma-gamma geophysical well logging applied to the exploration of minerals presents some peculiarities. These peculiarities are due to the ambiguity of density readings between different rock types, both iron formations and surrounding rocks and igneous intrusions, and the direct relation between the measurement quality conditioned by the characteristics of the rock mass. Specifically, the rock mass may be loose or compact, of more or less homogeneous composition, and include structural features throughout the borehole or mechanically induced stress caused by the geological drilling activity.
Thus, for gamma-gamma well logging data to be used systematically, the ability is needed to distinguish sections with good signal recovery from those whose measure is affected by operational and geological conditions.